Co-C bond energies in adenosylcobinamide and methylcobinamide in the gas phase and in silico.

Essential to biological activity of adenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl) is the Co-C bond cleavage step. Hence, we report an accurate determination of the homolytic gas-phase Co-C bond dissociation energies in the related adenosyl- and methylcobinamides (41.5 ± 1.2 and 44.6 ± 0.8 kcal/mol, respectively) utilizing an energy-resolved threshold collision-induced dissociation technique. This approach allows for benchmarking of electronic structure methods separate from (often ill-defined) solvent effects. Adequacy of various density functional theory methods has been tested with respect to the experimentally obtained values.

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